A generic device of that kind comprises a housing with an electric heating disposed therein, having a heating element and a heat exchanger, to supply the heat generated by the heating element to the heat exchanger and to convey the heat to the substance to be vaporized.
The object of the invention is to further develop a device of that kind so that it can be easily manufactured and works at low electrical power loss.
This object is achieved by a device comprising the features of The solution according to the invention is characterized in that the heating element is a PTC element, clamped between two electrodes, and that at least one of the two electrodes is disposed in proximity to the heat exchanger and is integrally formed therewith.
By providing the heating, it is achieved that the electrodes for the electric heating element at the same time serve the purpose of supplying the heat released by the heating element to the heat exchanger. Since the electrodes are integrally formed with the heat exchanger, the device consists of only few parts, so that the device can be easily manufactured at low cost. Furthermore, the device according to the invention has a good heat conductivity between the heating element and the heat exchanger so that the power loss can be kept low.
In one embodiment, the device comprises a container connectable to the housing for the substance to be evaporated, in which a wick is disposed, and the heat exchanger comprises a passage channel which surrounds the wick.
The heat exchanger is preferrably provided annularly, having a molded section, extending coaxially to the wick. In this embodiment of the heat exchanger, a good coupling of the heat to the wick takes place, which results in a good efficiency of the device.
In an alternative embodiment, the heat exchanger is provided as a planar heating surface, which serves as a supporting surface for a container for the substance to be evaporated. In this embodiment, a direct influence of the heat released by the heat exchanger on the entire substance to be evaporated is enabled by the direct proximity of the container to the heating surface.
The electrodes and/or the heat exchanger are preferrably provided with connecting conduits integrally formed therewith. By integrally forming the electrodes, the heat exchanger and the connecting conduits, the number of parts is reduced, which simplifies the manufacture of the device, since the conventional strand connections can be avoided and almost all electric parts can be manufactured on a common punch member.
It is of advantage if the connecting conduits, the heat exchanger and the electrodes are integrally formed on a punching sheet, which is bent if necessary after punching, and which is coated by a plastic material at the points at which an increased inherent stability or heat insulation is required. This considerably simplifies the manufacture of the device, since all parts can be manufactured from a planar workpiece by use of production machines.
In a further preferred embodiment, a region having a reduced wire cross section is provided between the connecting conduits and the electrodes or the heat exchanger, said region providing a sufficient electrical contact for the electrodes, but hardly conducts the heat. Thereby a loss of heat through the connecting conduits is avoided to a great extent.
In a further embodiment of the invention, the electrodes are surrounded by the plastic material on the sides opposite one another, and comprise a web on the sides facing one another at the outer edge of the electrodes. The PTC element disposed between the electrodes is thereby held in form-fit fashion between the webs, so that additional holding elements for the heating element are not necessary.
Preferrably, a resilient element is disposed between an electrode and the PTC element, and a clamping element clamps the two electrodes and the PTC element disposed between the two electrodes. In this arrangement, a close contact of the electrodes to the PTC element is achieved, which not only leads to a tight electrical connection, but also improves the heat coupling between the heating element and the electrodes.